A new scientific publication1 in the Beilstein Journal of Nanotechnology on 25 March 2024 presents results of analytical testing on the particle size of titanium dioxide (TiO2) and how to obtain reliable and repeatable results using electron microscopy. This is crucial for safety regulations as the particle size determines whether TiO2 meets the European Union (EU) recommended definition of a nanomaterial2 or a nanoform under the EU REACH regulations3.
Many scientific studies and publications refer to all TiO2 being a nanoform but only 2% of TiO2 is placed on the market as a TiO2 nanoform. The vast majority of TiO2 used in applications such as paints, plastics, paper, food and medicines is pigmentary TiO2 which has a much larger particle size. This larger particle size is important because it allows TiO2 to scatter light effectively resulting in an unrivalled pigment. In contrast, TiO2 nanoforms have limited light scattering ability and are not useful as a pigments.
The publication outlines a number of methods to improve the accuracy of particle size measurements and ways to validate the results. The main conclusion is that proper sample preparation before measurement is crucial, and the publication provides guidance on this. The authors, experienced analytical chemists, emphasise that particle size is also important in manufacturing TiO2 to ensure it is optimised for specific applications.
The TDMA are pleased that this has been published and hope it will lead to more widely accepted reproducible methods of measurement.
1Theissmann, R.; Drury, C.; Rohe, M.; Koch, T.; Winkler, J.; Pikal, P. Comparative electron microscopy particle sizing of TiO2 pigments: sample preparation and measurement. Beilstein J. Nanotechnol. 2024, 15, 317–332. doi:10.3762/bjnano.15.29
2European Commission. Commission Recommendation of 10 June 2022 on the definition of nanomaterial (2022C 229/01). s.l. : Official Journal of the European Union, 2022.
3Regulation (EU) 2018/1881 of 3 December 2018 amending Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). Official Journal of the European Union, 2018